Before the advent of evidence-based medicine, a huge variety of quack nostrums and dubious cures flourished. Many of these have faded away with time – and in cases like radioactive water, this was almost certainly for the best. However, some superstitious treatments that predate scientific medicine are still being used today. One of the most prominent is homeopathy.
Invented by Samuel Hahnemann in the early 1800s, homeopathy claims that “like cures like”: a substance that produces symptoms of disease in a healthy person will cure those same symptoms in a sick person. (By this principle, one would assume that the homeopathic cure for a person who has been shot is to shoot him again.)
However, it’s not as simple as just administering these substances to the sick person. Instead, they must be successively diluted – adding one part remedy to nine parts water, mixing, adding one part of the resulting solution to nine parts water, and so on – repeating this process many times until, by our subsequently acquired understanding of atoms and molecules, there is not even one molecule of the original substance left. Not to worry, though, because homeopaths claim that the water “remembers” what used to be dissolved in it, so that the process of dilution actually increases rather than decreases the remedy’s effectiveness. (Incidentally, homeopathy also claims that that all illness comes from internally originating “derangement of the vital force’s normal harmonious vibratory frequency“, and that the “vibrational pattern” of the remedy is what gets the body back into shape.)
There is absolutely no rational basis by which this could work. Everything we have learned in the last two hundred years about how the world works rules this out, and if homeopathy could be shown to have significant curative effects, then practically everything we thought we knew about the laws of physics and the human body would have to be thrown out. However, there is no such effect. Large, well-designed studies routinely find that homeopathy is useless. Skeptico, for example, links to a Lancet review of 110 clinical trials which concluded that homeopathy does no more good than a placebo.
I don’t know for certain how Hahnemann came up with the idea of homeopathy, but based on how it’s claimed to work, I think I can offer a plausible speculation. Here’s what probably happened:
Searching for a new method of curing diseases, Hahnemann at first guessed that a toxic substance which produced symptoms in a healthy person would cure a disease with those same symptoms in a sick person. This approach did not work, and naturally it had terrible side effects. In a bid to remove these side effects while keeping the presumed curative effects, he tried a variety of experiments. One of these experiments entailed successively greater dilutions of these substances. Unbeknownst to him, he had actually diluted his formulas to the point where none of the active ingredient was left. (Avogadro’s work on molarity and molecules was not published until over fifty years later.) But when he administered the result to patients, they showed improvement without showing any of the harmful side effects.
Nevertheless, homeopathic medicine was a hit, and it is easy to see why. In Hahnemann’s era, the scientific approach to medicine was rudimentary at best. Treatments were based on old, discredited superstitions such as the theory of the four bodily humors, and many of them, such as bloodletting, were actively harmful. Compared to these, Hahnemann’s approach was an improvement because it simply did nothing, allowing the body’s natural recuperative powers to work without interference.
Of course, we now have far more effective treatments that do not cause unnecessary harm, so there is no longer any good reason to rely on homeopathic medicine. And in any case, the idea that water “remembers” what substances it has come in contact with was absurd from the beginning. It is a particularly silly bit of magical thinking, and the logical gaps in the idea should have been obvious even in Hahnemann’s day.
For example, during the process of preparation, how does the water “know” which substance it is supposed to concentrate? In addition to whatever the homeopath chooses to add to it, any reasonable volume of water, no matter how pure or filtered, is bound to contain at least minute quantities of all kinds of toxins and contaminants – bacterial proteins, viruses, insect secretions, human and animal skin cells, heavy metals, natural radionuclides, pesticides, fertilizers, arsenic, asbestos, industrial byproducts, and so on. (See this list from the EPA). Are we to believe that water can somehow tell the difference between the one remedy the homeopath adds to it and all the other dissolved molecules it contains, and selectively amplifies only the former?
On the other hand, what if the homeopathic preparation of water does indeed amplify the curative properties of every substance dissolved in it? In that case, the probability is very good that any reasonably sized body of water will naturally have come in contact with some or all of homeopathy’s chosen remedies at some point in the past. By homeopathic principles, the more dilute the remedy, the more concentrated its curative effect. Therefore, it follows that any glass of water must be a homeopathic panacea, already containing an extremely dilute and therefore highly effective version of any “remedy” one would care to name. It seems pointless, therefore, for homeopaths to waste their time and money stocking medicine cabinets with specially prepared remedies for different types of disease. Whenever they feel ill, all they should have to do is drink a glass of tap water, and they should be cured of whatever afflicts them. But this would not generate much revenue for homeopathic practitioners, so it is probably not surprising that they do not talk about this.
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